This invention relates to a device for emitting light diverging along an imaginary plane.
Japanese Laid-Open Patent Application No. 53-133048 and Japanese Laid-Open Utility Model Application No. 61-179528 discloses devices for emitting light diverging along an imaginary plane. More specifically, this light emitting device comprises a light source, a convex lens and a cylindrical lens which are disposed on a common straight line. The light source emits light diverging along an optical axis. The convex lens converges the light, fed from the light source, so as to focus this light on a spot spaced apart from the convex lens. The axis of the cylindrical lens is disposed perpendicular to the optical axis of the convex lens. The cylindrical lens converts the light, fed from the convex lens, into light diverging along an imaginary plane disposed perpendicular to the axis of the cylindrical lens. The light from the cylindrical lens reaches an object to be inspected (this object intersects the imaginary plane), and appears as a line on the object to be inspected. By observing this line at an inspection position, the shape of the object to be inspected can be recognized.
In some cases, it is required to emit light which diverges along an imaginary plane parallel to a flat surface, and besides sometimes, it is required that the spacing between the imaginary plane and the flat surface should be as small as possible. The above conventional light emitting devices can not meet these requirements. More specifically, the light source, the convex lens and the cylindrical lens must be contained or housed in a casing, though this is not described in the above publications. Therefore, the minimum value of the above spacing is determined by the sum of the diameter of the convex lens (or the light source) and the thickness of the peripheral wall of the casing surrounding the convex lens and the light source. Thus, to narrow the spacing is limited.